Add a Schedules screen to manage recurring agents (#1246)

* feat: add Schedules screen to manage scheduled agents

Adds a Schedules section in the sidebar header (below Sessions) for viewing
and managing new-agent schedules: recurring jobs that spawn an agent on a
cron or interval cadence.

- Borderless table showing provider icon, model, cadence, next run, and
  status, with row actions to edit, pause/resume, run now, and delete.
- Create/edit sheet that reuses the agent provider/model/mode/working-
  directory pickers, plus an interval/cron cadence editor with presets,
  validation, and a UTC preview.
- Responsive: hover-revealed row actions on desktop, an always-visible
  action menu on mobile.
- Data layer over the existing schedule RPCs (list/create/update/pause/
  resume/delete/run-once) with optimistic pause, resume, and delete.

Scope is limited to new-agent schedules for now.

* Make the schedule form controls visually consistent

Merge the provider and model pickers into the single nested selector the
draft screen uses, render it as a full-width field, mute the placeholder,
proportion the cadence segmented controls, unify the cron preset chips,
and route the sheet scroll through the themed scrollbar.

* Address schedules review feedback

* Translate schedule hook client fallback errors

* Make schedules global and project scoped

* Stabilize project settings transport E2E

* Reset schedule model on cross-host project change

* Reject malformed cron step expressions

* Tighten schedules project query freshness

* refactor(schedules): clean up review feedback

* test(schedules): extract fake host setup

* refactor(schedules): share cron expression parsing

Use one structural cron parser for app previews and daemon cadence validation so the accepted grammar cannot drift between surfaces.

Remove the unused host-scoped schedules redirect while keeping the global schedules route.

packages/app/src/provider-selection/resolve-agent-form.ts

@@ -90,6 +90,7 @@ export type AgentFormAction =
       modelId: string;
       availableModels: AgentModelDefinition[] | null;
     }
+  | { type: "CLEAR_PROVIDER_SELECTION_FROM_USER" }
   | { type: "SET_THINKING_OPTION_FROM_USER"; thinkingOptionId: string }
   | { type: "SET_WORKING_DIR"; value: string }
   | { type: "SET_WORKING_DIR_FROM_USER"; value: string }
@@ -565,6 +566,24 @@ export function resolveAgentForm(
       };
     }
 
+    case "CLEAR_PROVIDER_SELECTION_FROM_USER":
+      return {
+        form: {
+          ...state.form,
+          provider: null,
+          model: "",
+          modeId: "",
+          thinkingOptionId: "",
+        },
+        userModified: {
+          ...state.userModified,
+          provider: true,
+          model: true,
+          modeId: true,
+          thinkingOptionId: true,
+        },
+      };
+
     case "SET_THINKING_OPTION_FROM_USER":
       return {
         form: { ...state.form, thinkingOptionId: action.thinkingOptionId },